Neurocognitive impairment in childhood-onset systemic lupus erythematosus: measurement issues in diagnosis.

OBJECTIVE: To assess the prevalence of neurocognitive impairment (NCI) in childhood-onset systemic lupus erythematosus (cSLE) by comparing published classification criteria, and to examine associations between NCI, disease characteristics, psychosocial well-being, and intelligence.
METHODS: cSLE patients and ethnicity- and age-matched healthy controls completed a neuropsychological research battery, and results were categorized by 3 different NCI classification criteria with different cutoff scores (e.g., >2, 1.5, or 1 SD below the mean) and the number of required abnormal tests or domains.
RESULTS: Forty-one cSLE subjects and 22 controls were included. Subjects were predominantly female (~70%) and Hispanic (∼70%). Executive functioning, psychomotor speed, and fine motor speed were most commonly affected. Method 1 classified 34.1% of cSLE subjects with NCI compared to method 2 (14.6% with decline and 7.3% with NCI) and method 3 (63.4% with NCI). The prevalence of NCI was not significantly different between the controls and patients using any of the categorization methods. NCI was not associated with SLE disease activity or characteristics or with depression. Using method 3, patients in the cognitive impairment group reported significantly lower quality of life estimates (69.7 versus 79.3; P = 0.03). Below average intellectual functioning (intelligence quotient <90) differentiated the number of test scores >1 and >1.5 SDs, but not >2 SDs below the mean.
CONCLUSION: NCI was prevalent in cSLE, but varied according to the chosen categorization method. A similar proportion of cSLE patients and controls had NCI, reinforcing the importance of studying an appropriate control group. Categorical classification (i.e., impaired/nonimpaired) may oversimplify the commonly observed deficits in cSLE.